The follicular phase is the first stage of the menstrual cycle, when an ovarian follicle gets ready for ovulation. The follicular phase usually begins on the first day of your period and lasts until about day 14 in a typical 28-day cycle.
During the follicular phase, the pituitary gland releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH). At this stage, FSH is especially important because it helps stimulate the growth and development of the ovarian follicles, which contain the eggs.
The length of the follicular phase can vary from one person to another. Hormonal problems, diet, age, oral contraceptive use, physical activity level, and stress can all affect how long this phase lasts.